Pakistan’s population constitutes approximately 2.65% of the world’s total population according to recent UN estimates. This makes Pakistan one of the most populous countries globally. Population statistics are important for planning economic development, resource allocation, and policy-making. A large population also presents both opportunities and challenges, including workforce potential and pressure on resources. Thus, 2.65% is the correct answer based on recent demographic data.

Red blood cells (RBCs), also known as erythrocytes, have an average lifespan of about 120 days in the human body. They are responsible for transporting oxygen from the lungs to tissues and carrying carbon dioxide back to the lungs for exhalation. RBCs lack a nucleus and most organelles, which allows more space for hemoglobin but limits their ability to repair themselves. Over time, they become less flexible and are eventually removed from circulation by the spleen and liver. The body continuously produces new RBCs in the bone marrow to replace the old ones. This balance ensures a stable supply of oxygen to tissues. Other options such as 45, 125, and 145 days are incorrect as they do not match the established average lifespan. Thus, 120 days is the correct answer. This concept is important in understanding blood physiology, anemia, and overall human health.

Qadirpur Gas Field, located in Sindh, is the second largest gas field operated by Oil and Gas Development Company Limited (OGDCL) in Pakistan. It was discovered in 1989 and plays a major role in supplying natural gas for domestic and industrial use. The largest gas field in Pakistan is Sui, located in Balochistan, which makes it incorrect for this question. Qadirpur follows as the second largest and contributes significantly to energy production. The gas extracted from Qadirpur is used for electricity generation, fertilizer production, and household consumption. Its development has helped strengthen Pakistan’s energy security. Kohat and Gwadar are not major gas fields under OGDCL. Therefore, Qadirpur is the correct answer. Understanding such fields is important for exams and also provides insight into Pakistan’s energy resources and economic development.

Sulphur dioxide causes corrosion by forming sulphuric acid in presence of moisture, damaging iron and steel structures over time. It accelerates rusting and weakens metal integrity, especially in polluted industrial environments.

The Rio Earth Summit, formally called the United Nations Conference on Environment and Development (UNCED), was held in June 1992 in Rio de Janeiro, Brazil. It was one of the largest international gatherings focused on environmental issues and sustainable development. The summit produced several key outcomes, including Agenda 21, a comprehensive plan for sustainable development; the Rio Declaration, which outlines principles for environmental protection; and major conventions on climate change and biodiversity. These agreements laid the foundation for modern environmental policy and global cooperation. The summit emphasized the concept of sustainable development, which balances economic growth with environmental protection. It highlighted the responsibility of nations to protect natural resources while promoting development. Other dates listed are incorrect because the conference specifically took place in June 1992. It remains a landmark event in environmental history. Thus, June 1992 is the correct answer, representing a pivotal moment in global environmental awareness and policy-making.